Search results for "Signal processing"
showing 10 items of 2451 documents
Theory of bound polarons in oxide compounds
2001
We present a multilateral theoretical study of bound polarons in oxide compounds MgO and \alpha-Al_2O_3 (corundum). A continuum theory at arbitrary electron-phonon coupling is used for calculation of the energies of thermal dissociation, photoionization (optically induced release of an electron (hole) from the ground self-consistent state), as well as optical absorption to the non-relaxed excited states. Unlike the case of free strong-coupling polarons, where the ratio \kappa of the photoionization energy to the thermal dissociation energy was shown to be always equal to 3, here this ratio depends on the Froehlich coupling constant \alpha and the screened Coulomb interaction strength \beta.…
Exact reconstruction of thz sub-λ source features in knife-edge measurements
2013
The spatial features of a sub-wavelength terahertz source are not accessible using time-integrated knife-edge techniques due to the non-separable space-time nature of the radiated field and to systematic modifications induced by the blade itself. We show that combining knife-edge with a time resolved electro-optical sampling, the space-time coupling can be addressed and the source field profile can be exactly reconstructed.
Coupling MCNP-DSP and LAHET Monte Carlo Codes for Designing Subcriticality Monitors for Accelerator-Driven Systems
2001
The design of reactivity monitoring systems for accelerator-driven systems must be investigated to ensure that such systems remain subcritical during operation. The Monte Carlo codes LAHET and MCNP-DSP were combined together to facilitate the design of reactivity monitoring systems. The coupling of LAHET and MCNP-DSP provides a tool that can be used to simulate a variety of subcritical measurements such as the pulsed neutron, Rossi-α, or noise analysis measurements.
Amplitude Analysis of Ds+→π+π0η and First Observation of the W -Annihilation Dominant Decays Ds+→a0(980)+π0 and Ds+→a0(980)0π+
2019
We present the first amplitude analysis of the decay D_{s}^{+}→π^{+}π^{0}η. We use an e^{+}e^{-} collision data sample corresponding to an integrated luminosity of 3.19 fb^{-1} collected with the BESIII detector at a center-of-mass energy of 4.178 GeV. We observe for the first time the W-annihilation dominant decays D_{s}^{+}→a_{0}(980)^{+}π^{0} and D_{s}^{+}→a_{0}(980)^{0}π^{+}. We measure the absolute branching fraction B(D_{s}^{+}→a_{0}(980)^{+(0)}π^{0^{(}+)},a_{0}(980)^{+(0)}→π^{+(0)}η)=(1.46±0.15_{stat}±0.23_{sys})%, which is larger than the branching fractions of other measured pure W-annihilation decays by at least one order of magnitude. In addition, we measure the branching fracti…
Simultaneous Measurement ofβ−Decay to Bound and Continuum Electron States
2005
We report the first measurement of a ratio {lambda}{sub {beta}{sub b}}/{lambda}{sub {beta}{sub c}} of bound-state ({lambda}{sub {beta}{sub b}}) and continuum-state ({lambda}{sub {beta}{sub c}}) {beta}{sup -}-decay rates for the case of bare {sup 207}Tl{sup 81+} ions. These ions were produced at the GSI fragment separator FRS by projectile fragmentation of a {sup 208}Pb beam. After in-flight separation with the B{rho}-{delta}E-B{rho} method, they were injected into the experimental storage-ring ESR at an energy of 400.5A MeV, stored, and electron cooled. The number of both the {sup 207}Tl{sup 81+} ions and their bound-state {beta}{sup -}-decay daughters, hydrogenlike {sup 207}Pb{sup 81+} ion…
Study and implementation of a soft X-ray 100 eV -20 keV fixed exit monochromator system
2006
We describe a “built in house” X-ray monochromator which produces a fixed exit X-ray beam tunable in the full energy range 0.1 - 20 keV. The system is based on a double diffraction on two large size parallel crystals positioned using a remotely controlled micropositioning system in order to keep the position of the monochromatic beam for any chosen energy. Up to six different diffracting elements can be selected without breaking the vacuum. This allows to cover the full energy range of interest. The system is part of an upgrading project of the XACT facility at the Istituto Nazionale di Astrofisica - Osservatorio Astronomico di Palermo G.S. Vaiana, and will be employed for the testing and c…
Hybrid (refractive-diffractive) Fourier processor: A novel optical architecture for achromatic processing with broadband point-source illumination
1998
We report on an achromatic Fourier processor constituted basically by a quasi-wavelength-independent imaging forming system whose first half performs an achromatic Fourier transform of the colour input. The novel optical architecture, only formed by a small number of diffractive and refractive lenses, works under white-light point-source illumination and provides an intermediate achromatic real Fraunhofer plane and a final colour image without chromatic distortion. In this way, our optical processor performs simultaneously, with a single filter, the same spatial filtering operation for all the spectral components of the broadband illumination. The practical capabilities of our proposal are …
Implementation and Performance of the Signal Reconstruction in the ATLAS Hadronic Tile Calorimeter
2012
AbstractThe Tile Calorimeter (TileCal) for the ATLAS experiment at the CERN Large Hadron Collider (LHC) is currently taking data with proton-proton collisions. The Tile Calorimeter is a sampling calorimeter with steel as absorber and scintillators as active medium. The scintillators are read-out by wavelength shifting fibers coupled to photomultiplier tubes (PMT). The analogue signals from the PMTs are amplified, shaped and digitized by sampling the signal every 25ns. The TileCal front-end electronics allows to read-out the signals produced by about 10000 channels measuring energies ranging from ∼30 MeV to ∼2 TeV. The read-out system is designed to reconstruct the data in real-time fulfilli…
The ATLAS TileCal read-out drivers signal reconstruction
2009
TileCal is the hadronic calorimeter of the ATLAS experiment at the LHC collider at CERN. The Read-Out Drivers (ROD) are the core of the off-detector electronics. The main components of the RODs are the Digital Signal Processor (DSP) placed on the Processing Unit (PU) dautherboards. This paper describes the DSP code and its performance with calibration and real data. The code is divided into two different parts: the first part contains the core functionalities and the second one the reconstruction algorithms. The core acts as an operating system and it controls the configuration, the data reception, transmission, online monitoring and the synchronization between front-end data and the Trigge…
Harmonic solution of semiconductor transport equations for microwave and millimetre-wave device modelling
2004
The transport equations for charges in a semiconductor have been solved for a periodic voltage excitation by means of a harmonic approach, for modelling of microwave and millimetre-wave active devices. The solution is based on the expansion of the unknown physical quantities in Fourier series in the time domain, and on the discretisation in the space domain. A Waveform-Balance technique in the time domain is used to solve the resulting non-linear equations system. In this way the time step is determined only by Nyquist's sampling requirements at the operating frequency, irrespective of the relaxation times of the semiconductor. This approach allows for a longer time step, and therefore a sh…